1. Field of the Invention
The invention relates to compressed air systems in industrial plants. Normally, air from the plant main supply line is continuously applied under pressure to each of the many control valve systems in the plant. A typical control valve system might be for dual acting cylinders which control clamping, piercing or other machine tool operations.
As long as the operator is using the machine, there is no harm in maintaining a constant supply of pressurized air to the machine control valve system. However, if the operator is not at his station for an extended period, for example, during a lunch break or overnight, the continuous application of compressed air through the machine control valve system results in energy wastage by the constant and inevitable leakage from the couplings, joints and valves.
2. Description of the Prior Art
A search on the subject matter of this invention revealed U.S. Pat. No. 3,729,024 wich shows the concept of shutting down a plant when a lubricator is not operating fast enough, the lubricator supplying air to an accumulator. However, the system shown in this patent would be unsuitable for accomplishing the purposes of the present invention and the patent fails to disclose important features as set forth in the attached claims. Another patent, U.S. Pat. No. 1,947,727, exemplifies other systems where, after a given time, a shift is made unless some other action is taken, this patent pertaining to the closure of an elevator door.